#rtl_sdr

I have no money for a real spectrum analyzer but I expect to have the need for it.

So I took an old DVB-T USB stick which can be used as a quite universal Software Defined Radio (SDR). I don’t need to demodulate what the SDR (USB stick) receives, so let’s make a quick solution here.

On http://dekar.wc3edit.net/2012/09/30/osx-port-of-the-awesome-gqrx-sdr-software/ there’s an easy-to-use (and install) graphic front end called gqrx for the USB stick. Downloaded the DMG file for MAC OS X from there and installed it.

Didn’t work.

I startet the application gqrx, set it up to default values, and after that, the application wouldn’t do anything more.

So I opened a terminal window and startet the application rtl_tcp first.

After that, I restarted the gqrx application. As expected, it was then able to connect to rtl_tcp and thus access the USB stick.

Now, what did I want to do with it: I’m trying to discover GSM technology, so the homepage on http://niviuk.free.fr/gsm_band.php a GSM frequency was found where there should be some signal.

Where this ARFCN of 4 came from? Used the field test mode on my Android smart phone. Type *#0011# into your Samsung Galaxy S3 phone and under the parameter BCCHFrq you find the ARFCN. So it was clear that on this channel / frequency I’ll find a signal.

Above you can see the result of gqrx when configured to look at the area around 935.6 MHz. As you can see, the cheap antenna was sufficient to receive the signal. Be sure to use “Filter=Wide" in gqrx.